This invention relates in general to audio-visual systems for recording and conveying information between people. More specifically, it relates to an automatic pointer mechanism that superimposes a highlight spot on a sequence of visual images, moves the pointer spot over the image under manual control in continuous coordination with an audio program, and records the movement controlling signals for automatic operation on playback.
A variety of audio and audio-visual systems record information presented by a speaker or operator and play it back to an audience of one or more people. Common commercially available systems include audio cassettes, slide/tape systems, x-y writers, video tape, and sound motion pictures. These systems have been widely used for teaching, maintenance training, advertising, entertainment and as instructional guides at museums.
Criteria for evaluating such information systems include cost, channel capacity, ease of use, visual animation, and correlation between the channels. Ordinary audio cassettes have a low cost, but they have no visual channel. Information transfer is relatively inefficient since the producer must create visual images with words. x-y writers, which can be used to reproduce a pen-on-paper drawing in coordination with an audio program, are convenient to use and convey information effectively. Their use is limited, however, to "blackboard" visual subjects, and their cost is high. Video tape and sound motion pictures are also effective communication media, but their cost is likewise high. As a result of these drawbacks, slide/tape systems are most frequently used for low cost, recorded person-to-person information transmission. However, one disadvantage of slide/tape systems is that there is visual stimulation only on changing the slides. Another disadvantage is that the correlation between the audio and the visual channels is typically poor since the speaker cannot readily and accurately direct the attention of the viewer to the portion of the slide image he is discussing.
One solution to these problems has been to use a pointer to direct attention to a portion of a slide. During a "live" presentation, the lecturer can simply point to portions of a slide image projected on a screen. U.S. Pat. Nos. 2,848,922 and 3,220,305 describe apparatus in which a manually-controlled movement of a bright spot superimposed over the slide image acts as a pointer. None of this apparatus, however, has a recording and playback capability. U.S. Pat. Nos. 3,522,037 to Stern and 3,804,503 to Sissom describe front screen projection systems in which signals from a prerecorded tape control a stepping switch which sequentially energizes fixed light sources that act as pointers.
British Pat. No. 1,435,510 to Faulkes describe a more flexible pointing system adapted for use with a sequence of front projected slides. A pointer device, including a light source, an apertured mask containing a slit, and a projection lens, projects an image of the slit on the screen. The signals for an audio program, slide change signals, and signals for controlling the movement of the pointer device are recorded in alternating sequence on magnetic tape. A manually controlled "joystick" is the position transducer that generates the pointer control signals during recording. These signals are demodulated and actuate two motor-driven cams that move the entire pointer device horizontally and vertically to shift the pointer image on the screen.
While the Faulkes system provides significantly greater flexibility and audio-visual correlation than the Stern or Sissom systems, it has significant shortcomings. First, the movement of the pointer image is not continuous and in parallel with the audio program; it alternates with the audio program. Thus, the Faulkes pointer mechanism is not capable of executing a continuous path on the visual image at the same time as the operator discusses it. The resultant sequential alternation between the audio and the visual channels, and a low level of visual stimulation, limit the communication effectiveness of the system. A second, related deficiency is that the Faulkes arrangement for moving the pointer, which is a key component of the system, is slow, insensitive and cumbersome. This is because the motor-cam arrangement shifts the entire pointer assembly, which has a comparatively high inertia. These characteristics do not lend themselves to an economical system for continuous and rapid pointer motion. Third, Faulkes provides no solution to problems associated with tape recording, such as variations in tape speed and particularly acceleration on start up, noise, drops in the signal strength ("drop out"), and start up at a random point in the tape due to a stop and restart or a power interruption. Fourth, Faulkes does not provide a system that can be readily mated to a standard slide projector, to a rear screen viewer, or to other media such as motion pictures and television. Finally, Faulkes does not address the parallax problems that arise when the visual image and the pointer spot originate from two spaced-apart sources and the projection distance is varied.
It is therefore a principal object of this invention to provide an automatic pointer system for a sequence of projected visual images that is movable continuously in close coordination with an accompanying recorded audio program.
Another object is to provide a pointer system that is highly simple and convenient to use, and which includes a manual control element that is held and manipulated with one hand so as to be particularly suitable for the recording of pointing motions in the course of a `live` lecture.
yet another object is to provide a pointer system that is of relatively low cost.
A further object is to provide a pointer system that is rugged and highly reliable and, in particular, is not susceptible to malfunction due to random restart, noise, dropout, power loss or tape speed variations.
Still another object is to provide a pointer system that is adaptable to a variety of audio-visual media and in particular operates with any commonly used slide projector.